1. Field of the Invention
This invention relates generally to the field of variable resistance devices and more particularly to ratcheting mechanisms for worm gear actuated potentiometers.
2. Description of the Prior Art
Worm gear actuated potentiometers have been known for some time. A common problem encountered in the construction of devices of this kind is in the method of provision of means by which excessive rotation of the driving element can be accommodated without damage to internal elements. In most applications it is necessary to provide a stop. Lacking such a stop provision, the resistance ratio may suffer discontinuous changes as a result of the travel of the wiper into and through open circuit conditions. Worm gear actuated potentiometers generally provided positive stops which prevent the wiper from rotating through such a distance as to lose contact with the resistance element. Thus the problem of discontinuous change of the resistance ratio was solved by limiting the wiper travel. Another problem, however, was thus generated because continued rotation of the drive screw after a limit stop was reached would cause stripping of the gears on the driven rotor carrying the wiper, thus causing destruction of the device. In some of the later devices, friction clutches were employed such that when the wiper reached a limit stop, the friction clutch would allow slippage so as not to damage the interior elements as a result of excessive rotation of the driving screw. Some of these devices, however, also allowed slippage under unpredictable conditions, thus operation became erratic and unreliable. Many different ratcheting devices have been employed in attempts to solve the problems presented. Most have either presented new problems or only partially solved the problems presented, or both. Most of these devices have thus met special needs as presented by specific problems and have therefore served narrow purposes. These prior art devices, among other disadvantages, have been unreliable and unpredictable in operation under continued use and have been expensive and complicated to manufacture. Some of these prior art devices have been described in the following listed patents that were brought to the attention of the applicant through a novelty search conducted in the United States Patent and Trademark Office
1. No. 3,497,856 -- "Adjustable Potentiometer" -- L. W. Scheel PA1 2. No. 3,242,452 -- "Clutch Means for Multiple Turn Variable Resistor" -- A. A. Grunwald, et al. PA1 3. No. 3,768,325 -- "Multiturn Adjustment Potentiometer Ratcheting Mechanism" -- L. Kucharski, Jr. PA1 4. No. 3,683,308 -- "Potentiometers" -- A. L. Hamill PA1 5. No. 3,569,896 -- "Ultrathin Miniature Potentiometer with Recessed Drive Means" -- W. D. Kirkendall PA1 6. No. 3,522,573 -- "Potentiometer Shaft Retention" -- R. Michik PA1 7. 3,522,572 -- "Gear Adjusted Potentiometer" -- R. Michik PA1 8. No. 3,208,024 -- "Potentiometer Construction" -- H. Enos et al. PA1 9. No. 3,099,810 -- "Miniature Potentiometer" -- H. Habereder PA1 10. No. 3,416,119 -- "Variable Resistance Control with Clutch Mechanism" -- J. Van Beuthuysen PA1 11. No. 3,115,614 -- "Miniature Potentiometer with Stop Mechanism" -- H. Habereder PA1 12. No. 3,701,070 -- "Worm Gear Actuated Potentiometer " -- K. B. Baldwin et al. PA1 13. No. 3,582,857 -- "Worm Driven Adjustable Potentiometer" -- J. F. Kishel PA1 14. No. 3,639,878 -- "Adjustable Potentiometer with Contactor Ratchet and Central Post Securing Means for Baseplate" -- L. W. Scheel PA1 15. No. 3,478,294 -- "Variable Resistor"-- W. D. Kirkendall PA1 16. No. 3,446,085 -- "Variable Resistor "-- L. Ginsberg PA1 17. No. 3,384,851 -- "Gear Adjusted Potentiometer"-- W. H. King PA1 18. No. 3,378,803 -- "Variable Resistance Potentiometer" -- C. Yungblut et al.
It would thus be a great advantage to the art to provide an improved ratcheting mechanism for a worm gear actuated potentiometer;
It would be another great advantage to the art to provide an improved ratcheting mechanism for a worm gear actuated potentiometer which is simple and inexpensive to manufacture;
A further desirable advantage to the art would be to provide a ratcheting mechanism for a worm gear actuated potentiometer which is predictable and reliable;
It would also be a great advantage to the art to provide a worm gear actuated potentiometer showing the advantages of ratcheting to prevent interior damage to the elements that will have a long operating life.